1. Field of the Invention
The present invention relates to a battery pack for use as a DC power supply for electrical machinery and apparatus and
1. Description of the Prior Art
A conventional battery pack, previously proposed by the assignee of the present application, will be described below (see Japanese patent application No. 3-52555).
FIG. 1 of the accompanying drawings shows a battery pack 10 attached to, and charged by a battery charger 12. FIG. 2 shows an example of the battery charger 12.
As illustrated, the battery charger 12 is a molded product of a plastic material and includes a concave portion 51 on which the battery pack 10 is attached. The battery charger 12 includes a primary circuit unit 52 having a power supply transformer or the like and a secondary circuit unit 53 having a rectifying circuit or the like. The battery charger 12 further includes an AC cord 54 with a plug connected to the primary circuit unit 52.
As shown in FIG. 2, the secondary circuit unit 53 includes a DC power supplying adaptor plug 55, charging power supplying first and second terminals 56, 57, and a temperature detection signal input third terminal 58. The adaptor plug 55 is provided so that the electrical machinery and apparatus can directly use the DC power from the AC power supply without using the battery pack 10.
The three terminals 56 to 58 are each formed of, for example, a plate spring so that they can be deformed with resilience. A spring constant of the third terminal 58 is substantially 2/3 of those of the first and second terminals 56, 57. As shown in FIG. 2, the first to third terminals 56 to 58 are assembled into a mold plate 60 which is disposed on the bottom surface of the concave portion 51. Such mold plate 60 is colored with some suitable color different from a color "black" of a case 59 of the battery pack 10, such as "blue" or the like.
Though not shown, the second circuit unit 53 includes a control circuit. The control circuit is operated to control the charging of the battery accommodated within the battery pack 10. This control done by the control circuit is based on a so-called -.DELTA.V charging completion method. That is to say, when the battery charging is started, a voltage between the first and second terminals 56, 57 is increased progressively. After the voltage reached to a peak value, the battery charging is ended when the voltage is decreased a little.
The aforesaid control circuit detects a temperature of the battery now being charged on the basis of a temperature detection signal from a temperature detecting element (not shown) disposed on the bottom surface of the battery pack 10. When a detected temperature exceeds a predetermined value, a charging current supplied from the first and second terminals 56, 57 to the battery is cut off and the charging done by the battery charger 12 is interrupted under the control of the control circuit.
As shown in FIG. 1, the battery pack 10 includes a case 18 that is formed of an upper case 14 and a bottom case 16 and is arranged such that a plurality of batteries are accommodated within the case 18.
FIGS. 3 and 4 show the battery pack 10 and the condition that columnar batteries 21 to 25 are accommodated in the inside of the battery pack 10. FIG. 3 shows the inside of the battery pack 10 with the bottom case 16 being removed, and FIG. 4 is a cross-sectional view taken along the line IV--IV in FIG. 3 and illustrating the battery pack 10, the batteries 21 to 25 and other elements and parts.
The batteries 21 to 25 might be nickel-hydrogen secondary batteries and are arrayed in a parallel fashion as shown in FIGS. 3 and 4. Electrodes of the batteries 21 to 25 are connected together via a conductive plate 32 and the five batteries 21 to 25 are arranged as a combined battery 27 in which the batteries 21 to 25 are electrically connected in series. An insulating sheet 34 is disposed between the electrodes of the batteries 21 to 25 and the conductive plate 32.
The combined battery 27 includes a first electrode 36 (positive electrode) and a second electrode 38 (negative electrode) for charging and discharging. On the under side of the two electrodes 36, 38, there are disposed a temperature detecting element 42 such as a thermistor or the like and a breaker (not shown). The first and second electrodes 36, 38, the temperature detecting element 42, the breaker (not shown) or the like are supported by a mold member 44 disposed between the two batteries 21, 22.
On the lower side of the battery 21 is disposed a third electrode 40 which derives a temperature detection signal. The third electrode 40 is formed as a thin plate to construct a plate spring and might be either directly bonded to the battery 21 by an adhesive or attached to the mold member 44.
The temperature detecting element 42 includes two lead wires 42A, 42B connected thereto. The temperature detecting element 42 is connected to the first electrode 36 by means of the first lead wire 42A and the temperature detecting element 42 is connected to the third electrode 40 by means of the second lead wire 42B. The combined battery 27 and the three electrodes 36, 38, 40 are disposed so as to come in contact with the inner surface of the upper case 14.
FIG. 5 shows a structure of a bottom surface of the case 18, i.e., an outer surface of the bottom case 16. The bottom case 16 has on its outer surface 11 concave portions 16A through 16K and three apertures 16a, 16b, 16c formed through its outer surface. The two apertures 16a, 16b are formed in the concave portions 16D, 16E, respectively.
The three apertures 16a, 16b, 16c are bored at the positions corresponding to the three electrodes 36, 38 and 40 of the battery pack 10. Therefore, when the case 18 is assembled by the upper case 14 and the bottom case 16 and the batteries 21 through 25 are disposed in the inside of the case 18, the three electrodes 36, 38 and 40 are exposed from the corresponding three apertures 16a, 16b, 16c, respectively.
The eight concave portions 16C to 16J and the two apertures 16a, 16b are disposed in association with spacings 28A through 28D between adjacent ones of the batteries 21 to 25.
As shown in FIG. 5, symbols +, -, .perp., encircled by open circles, are marked neighboring three electrodes on the outer surface of the bottom case 16. These symbols are formed by the embossing processing when the bottom case 16 is molded by a plastic material.
The whole bottom case 16 is colored with "black", for example, and a dashed-line portion 20 that encircles the three apertures 16a, 16b, 16c are colored with other colors such as "blue".
On the bottom surface of the concave portion 51 of the battery charger 12, there are formed convex portions 61A, 61B, 61C as shown in FIG. 2. The convex portions 61A, 61B, 61C are disposed so as to engage with the corresponding concave portions 16I, 16G, 16H of the battery pack 10.
The outside concave portions 16I, 16G of the concave portions 16I, 16G, 16H are referred to as detection apertures, and the inside larger concave portion 16H is referred to as a locking aperture. The detection apertures 16I, 16G function to detect whether or not the battery pack 10 is properly attached to the battery charger 12.
In the battery pack that can be properly attached to the battery charger 12, the two convex portions 61A, 61B are respectively inserted into the corresponding detection apertures 16I, 16G and the bottom surface of the battery pack 10 is brought in contact with the bottom surface of the concave portion 51 of the battery charger 12. Meanwhile, in the battery pack 10 that is not properly attached to the battery charger 12, the two convex portions 61A, 61B are not inserted into the corresponding concave portions 16I, 16G and the bottom surface of the battery pack 10 is raised from the bottom surface of the concave portion 51 of the battery charger 12.
The locking aperture 16H functions to lock the battery pack 10 so that the battery pack 10 attached to the battery charger 12 is prevented from being moved during the battery pack 10 is being charged.
When the proper battery pack 10 is attached to the battery charger 12, the three electrodes 36, 38, 40 of the combined battery 27 exposed from the apertures 16a, 16b, 16c of the bottom case 16 are brought in contact with the three terminals 56, 57 and 58 of the battery charger 12, respectively.
Since at least either the three electrodes 36, 38, 40 or the three terminals 56, 57, 58 are formed of members that can be deformed resiliently, such as plate springs, the connection of both of them can be made reliable under spring-biasing force of such resilient members. As earlier noted, the spring constant of the third terminal 58 is selected to be smaller than those of other terminals so that, even when the battery pack 10 having no third electrode is mounted on the battery charger 12, the bottom surface of the battery pack 10 can be protected from being damaged.
In the illustrated conventional battery pack, the detection apertures 16I, 16G are provided on the bottom case 16 of the battery pack 10. When it is determined whether or not the convex portions 61A, 61B formed on the bottom surface of the concave portion 51 of the battery charger 12 are engaged into the detection apertures 16I, 16G, it is determined whether or not the battery pack 10 is properly attached to the battery charger 12. The aforesaid arrangement can be applied to a relationship between the battery pack 10 and the battery charger 12 and also applied to a relationship between the battery pack 10 and the electrical machinery and apparatus that utilizes the battery pack 10 as a power supply thereof.
When the battery pack 10 is not properly attached to the battery charger 12, the battery pack 10 is raised from the battery charger 12 by a height corresponding to the convex portions 61A, 61B and then inclined. If this inclination angle is large, then it can be detected with ease that the battery pack 10 is not properly attached to the battery charger 12. Conversely, if this inclination angle is small, then it becomes difficult to detect whether or not the battery pack 10 is properly attached to the battery charger 12.
In order to increase the inclination angle, the height of the convex portions 61A, 61B of the battery charger 12 must be increased and the depth of the detection apertures 16I, 16G of the battery pack 10 must be increased. If so, it becomes difficult to mold the battery charger 12 and the bottom case 16.
In order to increase the inclination angle of the battery pack 10 without changing the height of the convex portions 61A, 61B of the battery charger 12, the convex portions 61A, 61B of the battery charger 12 and the detection apertures 16I, 16G of the battery pack 10 must be disposed nearer the central position.
However, in the example of the prior-art battery pack 10, as shown in FIG. 5, the detection apertures 16I, 16G are formed adjacent to one side portion of the bottom case 16 of the battery pack 10 and are not formed at the central portion of the bottom case 16.
Furthermore, the battery pack 10 includes an identifying marker (not shown) attached thereto to indicate that the battery pack 10 had already been used or charged. Such identifying marker is attached to a front end portion 16-1 (see FIG. 4) of the bottom case 16 of the battery pack 10. Consequently, the battery pack 10 is unavoidably increased in size in the longitudinal direction by the amount corresponding to the protruded portion of the identifying marker.
OBJECTS AND SUMMARY OF THE INVENTION
Therefore, it is a general object of the present invention to provide an improved battery pack in which the aforesaid shortcomings and disadvantages encountered with the prior art can be eliminated.
More specifically, it is an object of the present invention to provide a battery pack in which it can be detected with ease whether a battery pack is properly attached to a battery charger or a power supply of electrical machinery and apparatus.
According to a first aspect of the present invention, there is provided a battery pack having a battery accommodated therein which comprises a detection portion formed at a central portion of a bottom surface of the battery pack, the detection portion being engaged with an engagement portion formed on a connection portion of a battery charger or electrical machinery and apparatus to which the battery pack is connected to detect the kind of the battery.
According to a second aspect of the present invention, there is provided a battery pack having a battery accommodated therein which comprises a detection portion formed at a bottom surface of the battery pack, the detection portion being engaged with an engagement portion formed on a connection portion of a battery charger or electrical machinery and apparatus to which the battery pack is connected to detect an electric power output amount of the battery.
The above and other objects, features, and advantages of the present invention will become apparent from the following detailed description of illustrative embodiments thereof to be read in conjunction with the accompanying drawings, in which like reference numerals are used to identify the same or similar parts in the several views.